The present invention relates to a steering booster system for a motor vehicle, and more particularly, to a system in which an electronic control unit senses, via force or torque sensors, the amount and direction of forces and torques applied by a driver to a manual steering wheel and correspondingly controls, via a transmission arrangement, the steering-force-assisting connection of an electric motor into a steering gear line coupling the manual steering wheel and the steered vehicle wheels. The transmission arrangement has an electrically switchable clutch for each steering direction (left or right) are arranged such that, in the event of the same rotation direction at the input of the transmission arrangement assigned to the electric motor, they cause a different rotation direction at the output of the transmission arrangement assigned to the steering gear line. The electronic control system controls the amount of the steering force assistance by way of the slip of the respective clutch and/or by way of the torque of the electric motor.
In a known steering booster system, which normally is also called a power steering system, the manual steering force exercised by the driver on the manual steering wheel is detected by corresponding sensors and is analyzed in an electronic control unit. As a function of the manual force applied by the driver, the control unit will then determine the required steering force assistance and correspondingly control the electric motor of this power steering system.